The objectives of this study are: 1) to determine the effect of pancreas transplantation on hepatic glucose production and glucose turnover rates in type I diabetic recipients in the basal hypoglycemic states, 2) to evaluate whether successful pancreas transplantation will, over time, improve insulin sensitivity and glucose effectiveness in type I diabetic recipients, 3) to determine whether changes in substrate utilization, energy expenditure, and body composition occur due to the metabolic changes produced by pancreas transplantation.